Electric fuse.



c. w. DAVIS.

ELECTRIC FUSE.

' APPLiCATION FILED APR.22. 1913. 1,152,147. Patented Aug. 31, 1915.

L 6 6 I, r

l 7 I 8 1o 8 i9 v 20 1 t 21 {6 9 T -i ri Q UNITED STATES PATENT OFFICE.

CHARLES. 'W'. DAITIS, OF EDGEWORTH, PENNSYLVANIA, ASSIGNOIR. TO STANDARDUNDERGROUND CABLE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A COR,-

I PORATION E PENNSYLVANIA.

ELECTRIC F SE.

Specification of Letters Patent.

Application filed April 22, 1913. Serial No. 762,8 8 6.

To all whom it may concern .Be it known that I, CHARLES W. DAVIS,

. residing at Edgeworth, in the county of Allegheny and State ofPennsylvania, a citi- .zen of the United States, have invented ordiscovered a certain new and useful Imous; and has particularly to dowith fuses used in connection with high voltage currents.

It is sometimes desirable that the fusible portion 'of the currentcarrying element be relatively short to the end that there will be aminimum amountof resistance to the current and hence a minimum loss ofenergy due to such resistance. On the other hand it is desirable thatupon the blowing of the fuses the distance between the unconnected endsof the conducting element be relatively large so that arcing may bespeedily stopped.

To embody these desirable features in fuses it has been suggested toimpose a tension on the fuse strip, so that, when the short fusibleelement blows, the adjacent ends of the strip will rapidly separate andwiden the arc gap. In fuses for high voltage and low amperage currentsthe fusible. element must, particularly when surrounded by anarc-dampening liquid, be very small in cross-section and hence of lowtensile strength, so that, when heated, it is llable to rupture underits tensile strain before its rated current-carrying capacity has beenreached. Y

With these considerations in view it is the object of my presentinvention to provide a fuse structure wherein the conduct 'ing elementis free from tensile stress, but is of such a character, so far as itsphysical properties or shape is concerned, that its end connected tosuch fusible portion, will be bodily moved away from its normal positionby the exploslve force generated by the blowing of the fusible portion,such conducting element being surrounded by a cis- I 'ing adapted todirect said explosive force along the general line of the ductingelement.

In the accompanying drawing, which forms part of my specification, Ihave illustrated two embodiments of my invention.

unfused con- Patented Aug. 31, 1915.

Figure 1 of the drawing is a vertical sec-.

tional view of a junction box having two terminal-provided cablesentering therein, and a fuse connecting them, the casing for such fusebeing shown partly in longitudinal section and partly in elevation; Fig.2 is an end elevation of the fuse structure, the plane of view beingindicated by the line II.II, Fig. 1; and Fig. 3 is a longitudinalsectional view of a second form of fuse.

Like numerals are used to designate like parts.

While my invention is not limited to fuses immersed in an arc-dampeningliquid such as oil or carbon tetra-chlorid, the forms shown herein areparticularly well adapted for such use. Accordingly the fuse structureis shown in a junction box casing 1 filled with an arc-dampening liquidup to the level indicated by the line 2. Each entering cable 3 isprovided with a suitable terminal structure 4, which has at its outerend a knife-blade contact clip 5, and extending from each side of theterminal there is a guide post 6. Y

The complete fuse structure, as shown in Figs. 1, and 2, comprises asuitable frame or handle 7 of insulating material, having a yoke orgroove 8 ateach-end adapted to fit around the guide posts -6, andprovided at its lower edge with knife blade, contacts 9 adapted to tinto the contact clips 5. Extending laterally from and electricallyconnected to the knife blades 9, are arms 10, each provided at its outerends with laterallyprojecting ribs 11 and with a binding post 12. Anopen ended fuse casing 13 extends over and is supported by theribsll'and the fuse strip 14, 15 is connected at its opposite ends to thebinding posts 12.

As stated above the conducting.eleinent consists of two portions, a lowfusion portion and adjoining it a flexible high fusion portion, which isreadily distortable by the explosive or blowing force of the low fusionportion. In the particular embodiments of my invention illustratedherein, the low fusion portion 14 is centrally disposed withinpressure-resisting faces in the path of the fuse-explosion chamber. arepreferably placed on and borne by the portion 15 near the ends ofthefusible porexplosive force, and the central portion 14 being narrowerthan said end portions, and

consequently of less current-carrying capacity than the end portions.Itwill readily be seen that, when the portion Hfuses, the gas of fusionconfined by the casing wall will exert its pressure upon the severalfaces of end portions 15 and cause their unconnected ends to rapidlymove toward the end openings of the casing, thus diminishing theliability of ,a continuing arc.. In Fig. 3 the portions/15 consist ofvery flexible stranded conductors, which will likewise be forced towardthe ends of the casing 13 upon the blowing of the fusible portions 11,such fusible portion consisting either of one or more strands of suchconductors, or of a separate conducting element electrically 30connected to the ends of the portions 15.

In order to increase the conductor-moving effectiveness of the explosiveforce of the fuse, means may be provided within the casingand'surrounding the conductor strip for resisting such force. To such anend'two' abutments 16, preferably formed of a suitable insulatingmaterial, are borne by the strip 14, 15 of Fig. 1, such abutments beingreadily movable through the casing 13, and forming with the wall thereofa These abutments tion 14. In the embodiments of my inventionillustrated in .Fig. 3 substantially the same end is obtained bysecuring an abutment 16 to the casing 13 at the center of andsurrounding the fuse portion 14 In addition to directing the explosiveforce toward each end of the casing 13, the abutment 16 is alsoeffective to dampen out or diminish the size of the are formed when thefuse blows. In each embodiment of my invention it will be observed thatthe conducting ele'ment is unstressed, or, in other words, free fromtensile strain during the normal operation of the fuse.

While, as stated-above; the fuse structures shown herein areparticularly well adapted for use in a junction box partly filled withan arc-dampening liquid, my invention may be advantageously employed infuses wherein the fusible portion is not surrounded by such aliquid. Forexample, in the fuse particularly illustrated in Fig.

1, the fuse-explosion chamber formed by the central portion of thecasing 13 and the abutment 16 may be filled with an inert material, suchas slaked lime or magnesia; and, in case such inert material tends tobecome incandescent upon the blowing of the low fusion portion 11 of theconductor, the gas generated would rapidly separate said abutments andthus widen the gap between ing the force of the expelled liquid and fordeflecting such liquid away from the casing opening and into the body ofliquid withinthe box.

The means to this end, which I have illustrated herein, comprisedeflecting bells 17, preferably formed of insulating material andsecured to bars 18, which are yoked together by means of rods 19, the

entire structure being suitably supported in the junction box by meansof brackets 20. Each bell is placed with its concave side toward thecasing opening, and is provided with a central tapering projection 21,the point thereof being in line with the center of the casing opening sothat the expelled liquid will be turned away from such opening.

The operation of the fuse will be readily understood from its foregoingdescription. During the normal operation of the fuse, when submerged ina liquid, such liquid circulates through the open-ended casing, thukeeping the strip cool; the abutment 16 being small enough to permit ofsuch circulation. If desired, however, the casing 13 may be providedwith small openings 22 in order to facilitate the circulation of theliquid. In case the portion 14 blows, the liquid, being relativelynon-compressible, materially aids in the forcing of the free ends of theportion 15 away from each other. After the fuse blows the entire fusestructure may be readily removed by grasping the handle 7; and,structure to its operative position, the guide posts 6 are of asubstantial advantage.

I claim as my invention: p

1. In an electric installation, the combination of a junction box, apair of cables entering therein'each provided with a ter- .minalstructure, each of said terminals being provided with a contact elementand with guldes, and a removable fuse structure in returning the fuse 4adapted to electrically unite said terminal contact elements, saidstructure having as parts thereof guideways adapted to engage saidterminal guides.

2. In an electrical installation, the combination with a junction box,and electrical conductors therein, of a fuse strip electrically unitingtwo of said conductors, a casing surrounding said fuse-strip andprovlded with an expulsion opening, said casing and its containedconductor being submerged in an arc-dampening liquid, and.

means interposed between said casing opening and a wall of said junctionbox for resisting the force of the fluid expelled from saidcasing-opening upon the blowing of said fuse strip. I

3. In an electrical installation, the combination with a junction box,and electrical conductorstherein, of a fuse strip electrically unitingtwo of said conductors, a casing surrounding said fusestrip and providedwith an expulsion opening, said junction box being filled with anarc-dampening fluid above the level'of said fuse. casing, and V Y asingle means interposed between said casing opening and a wall ofsaidjunction box for resisting the force of the fluid expelled from saidcasing-opening and for deflecting said expelled fluid away from saidcasingopening upon the blowing of said fuse strip.

4. In; an electric fuse, the combination of a conducting stripcomprising an unstressed low fusion portion and an adjoining flexibleand readilydistortable high fusion portion, a casing surrounding saidstrip and provided with an expulsion opening, the flexible portion ofsaid strip being movable toward said opening solely by the explosiveforce generated by the blowing of said low fusion portion, and means forpreventing said flexible portion, when thus moved, from being expelledfrom the casing.

In testimony whereof I I have hereunto set my hand.

CHARLES w. DAVIS.

Witnesses:

PAUL N. CRITGHL W,

FRANCIS J. ToMAssoN.

